Steam generating system



' Filed March 4, 1939 4 Sheets-Sheet 1 llllll IIIII ITKIIII C. OCONNOR STEAM Dec. 29, 1942.

(:HNILRATTNG SYSTEM Filed March 4. 1939 4 Sheets-Sheet 2 r gzadwell O'Connor I fl/forzzgs Dec. 29, 1942. c, OCQNNOR 2,306,896

STEAM GENERATING SYSTEM Filed March 4, 1959 4 Sheets-Sheet 3 Jill/6722 0? C igzdwell O'Connor Dec, 29, W42. c. OCONNOR 2,306,395

STEAM GENERATING SYSTEM Filed March 4, 1939 4 Sheets-Sheet 4 Jhdenfo? r C /fad wefl O'Connor over the heat Patented Dec. 29, 1942 UNITED STATES ]PATENT- OFFICE 1 I "2,306,896 a STEAM GENERATING SYSTEM Chadwell O'Connor, Los Angel es, Calif. Application March 4, 1939, Serial No. 259,720

15 Claims. (Cl. 122-245) This invention relates to a novel steam genan improved method of generating steam.

One object of the invention is to provide a I novel method of and apparatus for generating steam including an improved steam generating unit of the water tube type adaptedto be operated at substantially higher thermal efliciency than has heretofore been practicable.

Another object is to provide an improved steam generating unit capable of operating at high and substantially uniform efllciency at any rate with- .in its capacity.

Another object is to provide a steam generating unit of the water tube type in which stagnation of water at the heating surfaces and consequent overheating of the latter is avoided.

- Still another object is to provide a steam gencrating unit of the above general character in when the unit is in operation, thus avoiding excessive strains due to unequal expansion with attendant weakening of the parts.

The foregoing objects are attained by reason of the 'novel and advantageous construction of the steam generating unit together withthe provision of means for effecting circulation of water transfer surfaces, at a substantially higher'velocity than is attainable by convection alone. More particularly, maximum efliciency means in a manner such that the water in association with such surfaces: is under sufiicient pressure to maintain its critical temperature above actual water temperature to minimize tube type in which I crating system and more particularly concerns a novel water tube steam generating unit and the heat transfer surfaces, heat absorption is effected with great eificiency.

' Still another object of the invention resides in the novel method of and means for separating the steam from the water 'without'surging, agitation or foaming even though circulation in the system has been greatly accelerated.

A further object of the invention is to provide a boiler of compact, easily accessible construction which will efiiciently utilize not only convected heat but also radiated heat and in which heat loss is maintained at a minimum. Ancillary to this,it is an object to'provide a construc-- tion such that even the heat escaping from. the

auxiliary equipment such as pumping mechanism and connecting pipes is utilized, as for preheating the air supply for the burners.

-A still further object of the invention is to provide a" novel boiler assembly wherein all parts are readily accessible with-a minimum of interference from or disturbance of adjacent or 00- acting parts and in which replacements can be effected easily and quickly. I

It is also an object of the invention to provide a highly eflicient arrangement of heating tubes "adapted for high velocity circulation of the water therethrough without the creation of back pres-.-

sure as steaming progresses, heat being abstracted with high efilciency fromthe combustion gases passing betweenthe coils in such amanner that the heat is transferred to the water in a uniform, progressive manner. An ancillary object is to mountv the heating coils in an improved manner to permit individual coil sections to be removed from and replaced in the assembly quickly and easily.

Additional objects of the'invention are to prov vide an improved multiple section insulated casas well as other advantages including those above 'set forth are attained by arrangement of the "heat' transfer surface and water circulating 'ing for enclosing the boiler designed to permit removal of individual sections for access to selected portions of the installation; to provide an improved water and steam chamber which will serve in addition as a mud drum, preheater and steam separating chamber; to provide improved means for effecting forced circulation in the system; and to provide a vertical boiler structure of industrial capacity requiring only very low headroom and very limited floor space, which will avoid the necessity for special settings or boiler pit and which is adapted to receive most taining water rather thansteam in contact with of the auxiliary equipment within a raised base below the main superstructure of the steam generating mechanism.

Other objects and advantages will become apparent in the following description and from the accompanying drawings in which:

Figure 1 is a side elevational view, partially in section, showing a steam generating unit embodying the principles of the invention.

Fig. 2 is a vertical sectional view through the unt taken substantially along line 2-2 of Fig. 1,

and having certain electrical features shown tion showing a further modification.

Fig. 7 is a sectional plan view taken substantially on the plane ofline 1-1 of Fig. 6.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail selected preferred embodiments, but it is to be understood that I do not thereby intend to limit the invention to the specific forms disclosed, but intend to cover all modifications and alternative or variant constructions and systerns falling within the spirit and scope of the invention as expressed in the appended claims.-

As a matter of convenience the'terrns water and steam have been used herein to designate the liquid medium which is converted into gaseous form in the operation of the system, but

these terms are intended to be generic and not restrictive in meaning and should be construed wherever possible, consistent with practicability, as covering any liquid medium that can be used for this purpose and its gas or vapor which will be formed in the practice of the method or use of the apparatus disclosed.

Generally speaking, the novel steam generating system of the present invention includes in a continuous cycle the steps of withdrawing water from a partially filled storage chamber or drum within which it may be thoroughly preheated.

impelling the withdrawn water into circulation. in contact with heat transfer surfaces, returning the heated water to the chamber to permit ex- 'pansion' and conversion of a portion thereof tosteam, and therein effecting separation of the steam and commingling of the unconverted water with make-up water, and recirculatingthe water in contact with the heat transfer surfaces. Pref erably, the velocity with which the water is c rculated and its pressure, while in contact with I the heat transfer surfaces, is such that only about one-third or less of the water is converted into steam upon its discharge into the steam chamber. In returning the water and generated steam to the drum, the steam is substantially all withdrawn in the upper water-free part of the chamber before the heated water is returned to the body of water therein, thereby relieving pressure from and avoiding gushing of the returned water and preventing agitation and foam ng in the body of water. In addition to preheating of the substantially constant head of the body of water in the drum by external means, the heated water which is separated from the steam and returned to the drum in the circulation cycle will serve as apreheating medium.

The invention may be practiced in connection I with and embodied in a preferred practical form of steam generating unit or boiler as shown by way of illustration in Figs. 1 to 4, inclusive, including an elongated vertical water and steam tank or drum l5 mounted centrally upon a base framework l6.- Water is conducted from the drum l5 under forced circulation through a pres- I sure duct II to a series of heating tubes, indicated generally by the numeral ",located about 10 the upper portion of the drum l5 .above and within the heating zone of a. suitable source of heat such as a plurality of any preferred form of gas burners iii. In the heating tubes is the water is raised to a temperature suitable for converting a portion into steam, the conversion into steam taking place upon its discharge into the upper part of the drum IS. A separator acts to bleed off orseparate the steam from the water.

20 Herein the drum [5 serves the multiple functions of water reservoir, preheater, mud drum, separating chamber and steam chest, thereby effecting substantial structural and space economy in the unit. Preferably a seamless cylindrical construction is employed in the drum IS,

the ends being suitably closed as by swedging, although heads could be secured to the ends of the tube body as by welding. The drum ends are preferably of concavo-convex shape to provide a dome l5 at the top and a dished bottom l5 which may serve as a mud sump. Access into the drum may be had through one or more removable clean out plugs 2| located adjacent to the bottom l5". Periodic cleaning out of mud deposited in the bottom I!" may be effected through a valve controlled blow-of! 22 leading from the pit of the bottom.

Any suitable means may be provided for supporting the drum l5 upon the base framework IS, an annular cradle 2! herein serving such purpose and preferably being secured fixedly to the lower end of the drum as by welding. The cradle 23 may have connecting flanges 24 by which it canbe secured detachably to a top platform 25 upon the base IS, the flanges being held down by bolts 28 so that when desired the drum I! may be removed from the base. I

In the preferred form, the base framework It is constructed 'of structural iron members suitably connected as by welding. In this framework, the top platform 25 is preferably supported by uprights or legs 21 in raised relation to a surface such as a floor 28 upon which the unit may be supported; Through this construction a.

substantial chamber is provided below the top 2| 1 to house auxiliary equipment for the boiler such as a feed water sump 28 which may be mounted upon a platform 30 carried the base frame legs 21 in spaced relation to the floor 2.. A waten supply pipe 31 leads to the sump 22 d is controlled by suitable float valve mecha w to maintain a substantial fixed level of water within the sump. From the sump. water is conveyed to the drum l5 througha delivery or feed duct 32 which discharges through the bottom II" and has its outlet end located a substantial distance above said bottom so as to project above mud that may accumulate thereon.

A constant head or body of water, partially filling the drum I5 is maintained by means of an intermittently operable feed pump 33 of suitable design suitably interposed in the feed water duct 32. A check valve II in the feed water duct prevents reverse flow of water from the drum ll.

5 When the water in the drum l5 falls below a fixed its ends to an electrode, 40

43. and a pressure gauge- .motor 31, the circulation v t I 31 ':.may be. mounted .upon the. lower platform 30 01' the, combustion gasesk from the transferred :to the water, .the we of! .valve 41' for segregatingthe pump -located in the outlet 45 to be manually controlled by a conveniently located M 'able' one-way.-.automatic, check valve 41 may be provided in-the lower end of athe riserj of in any one circulation cycle.

lava houghtless W t means will be operatedtoefiect operation or the P p l t h mea s n he,ni $en ta ;be f m electrically. controllediesponsive to fluctu ations in the waterle'vel andjincluding-a drIv-'- ing motor 31 for the pump.

at. entanglement-"1g taining a constant volume,

An electrical. control c rcuit for feed puma? motor 31 may include an electrical lead 38 have 39 therein andconnected at one? of ing. .a relay meu 'e hmiasma water regulator N I as thepreferred water lever 35... .The oftheelectrode-40mm; the wall'of the tank 4i which is suitably ground-f edland an electrical circuit through, the electrode and thetank s ervingto cutout the motor SIfis completedtonly when the water isat the proper level. 1 For 'thispurpose the, tank llmay be con nected in suitable manner toa conventional stand pipe which in turn. communicateskat its upper" and-lower. ends withfthe interior-{oi the drum iithrough thetop .l5 fandjthejbottom I5 'respectively.; Thus, when the waterleve1 ,,35 drops,

will take place in the regue a corresponding drop lator tank 4!, opening the, motor cut out circuit through the electrical lead. 38 so .1 that the water pump-motor 31 will operate to drive the water pump 33 andtherebyfimakeup" or replenish" the supply. of water inthedrumjl 5 The stand pipe I! may .also earrya conventional water gauge sary valves'lle- V According tothe present invention forced cyclical circulation of the -water isfeffected from'the drum l5 through the pressure. duct 1 and the heating tubesi8 and back through thedrum. To this end the'duct i1 Lhasa. suitable circulating pump [45 connected therewith and adapted to be actuated :by a suitable p'o'werj' means such as a v motor 31'. .Siniilarly'asithefeedpump'33 and its pump 45am its motor of the base under the steam generating'apparatus and high enoughj off oftthe Qfloor 2 8 to; permit cleaning thereunder as; by means of a streamfrom a water-hose.

Atubular outlet 46 projects upwardly throughthe bottom of the drum l5 substantially, above the mud sump fareafto-withdraw and conductthe wateriromthe drum-toone side, of ,the pump. from which the water is forced ata predeterminedIVelOcity through the 'remainderpof =-the pressure.ductl1 and then through the heating tubes. i'li a h rei thej heat burners I9 is being returned to the drumv i5. ,A'suitable shut- 45 may be handle 41?." A suit- ..the pressure duct t1 to segregat'e the pump' 45 therefrom.

Both the circulation ru ee pujmprs'end the feed water pump 33* have double stroke action.

- In the p r a iq the s mfs generating system the water drawn from the druml 5 is impelled" through the heating tubes "by the circulatingpump fl, supplemented by acceleration dueto perio'dic such a'velocity and in such volume that only ,steamfexpansion, at

enough heat will be absorbed by the water to ter thereafter tank A l and at thesame 'height' I k I inner end he; inspaced relation to circulated through the heating tubes while main-e consistent, of course, witheconomical pumping, the higherwill be the efliciency of the system. G0OdS results have been obtained in practice lation with such velocity that nomore than one part in about three of a unit volume of willbe converted into steam inone circulation cycle, the velocity in the. heating tubes .being roughly sixhundred feet per minute. In any" event the velocity should preferablytbe suchir speed of flow and the the tubes that due to the pressure created there will be relativelyf ittle steaming in the tubes but only heat absorption,

' the breaking into" steam occurring mainly when the-pressure is e-relieved outside of the'ftubes. Thus, itis' possible to circulate water continuously from' and back .to the drum. l5 ,with a, minimum of steaming until the water is returned from the heating'tubes to the drum. it will be se,that steam -f ormation .in y

understood, I of con; theheating tubes may be entirely eliminated if desired by suitable'uncreasing the water pressure "or velocity'or both; I

m the present instance, however, the pressure upon the water is periodically interrupted .in the circuit by diverting it from the tubes and then causing-it to flowon through-succeeding tubes of increased cross-sectional flow area .to .accor'nmodate' expansion arising from steam .iormed incident to the pressure drops. Preferably, however, the increase in flow areaof successive tubes or banksof tubes is somewhat less than the the- "oretical amount required to accommodate the full expansion of the circulating water so that the velocity of the water through such tubes increases progressively. This increase in velocity compensates for'the rise of temperature of the "water and thusprovides substantially uniform generally pansion occurs.

heat absorption throughout theentireseries of tubes. e

-As herein-shown. the enlarged flow area is attained by constructing the heatingtubes IB not only-to carry the water therethrough ina continuous series, but also in parallel passages "increasing in numberas periodic steaming ex- To this end the heating tubes l8 preferably comprise tubing of uniform pipe size formed into a plurality, of individual, cylindricalh'elical coil sections of such varying diameters and length that they can be mounted in concentric closely adjacent relation to form a cylindrical mass ofsubstantially uniform over-all length. The loops or helices of the individual coil sections are preferably, uniformly spaced one from the other and are held against springing by circumferentially spaced vertical rows of fixed heat-conductingspacers In the assembly, the helices of, each coil section placed in as nearly equally spaced as possible with respect are preferably, closely staggered relttion to the helices of the. immediately adjacent coil "section or sections (Fig. staggered relationship of the coils, practically every particle of the heated gases from the burn- 2). Due to this closely ers l9 that passes through the heating coil assembly will be baffled to travel in a turbulent circuitous'path and be in practically continuous convert asmall fraction of the water into steam I have found that the greater the velocity at which the 'wateris intimate heat transterrelation to coil helices from end to end of the coil assembly. Moreover,

because of the fairly densemass of the heating coils there is a throttling effect upon the heated gases which slowstheir travel sufficiently to assure all possibleheat abstraction by the waterswept coils. In' spite of such throttling of the by forcing ,the circu-' the water,

In the embodiment of the invention illustrated, there have been provided nine coil sections of equal pipe size and'of graduated diameters, progressively diminishing in pipe length corresponding to decrease in diameter so that each section may have nine equally spaced loops or helices in a predetermined standard length coil cylinder. These nine coil sections have been divided into three successive passes or banks connected in series to conduct the boiler water progressively from the outside to the inside of the cylindrical coil assembly. Thus, the boiler water is delivered .by the pressure duct l'i first to a pair of outermost coil sections 81 for travel therethrough in parallel paths, and is thence conducted through three parallel-flow intermediate coil sections 88 whence it will be conducted into four parallel-passage inner or final heating coil sections 89. The coil assembly is preferably located in closely embracing, concentric relation to the upper portion of the drum I5 so that, the combustion gases must pass upwardly therethrough from the burners [9. Furthermore, in order to secure the utmost thermal efilciency the water is caused to flow through each successive bank of coils. from the top downwardly, counterflow to the upflowing hot combustion gases. Through this arrangement, by utilizing approximately four hundred feet of standard three-eighths inch or one-half inch tubing in the heating coil assembly, may be had a steam generator of at least forty-five horse power normal capacity.

As a result of the counterflow of water and its high velocity heat will be practically exhausted from the combustion gases before they leave the heating coil assembly. However, the capacity for heat abstraction from top to bottom of the coil assembly will be almost uniform because of the continuous velocity of the water. Moreover, the increased heat transfer area of the successi e banks of coils and the acceleration of velocity assures uniformity of heat abstraction horizontally through the mass of coils. Another factor to be noted in this connection is that the progressive reduction in the lengths of the coils of the individual coil sections from the outer to the innermost due to diminution in diameter,

and thereby graduated reduction in heat transfer area. is compensated for by the successively increased number of coil sections in the banks of coils and also by the increased velocity of the water through the successive banks of coil sections.

All of'these observations have been determined from critical inspection and analysis in actual operation of the invention. If graphically represented, the heat absorption rate curve the remaining coil sections, and yet all of the distributed bubbles.

coil sections are preferably supported to be handled as a complete unit. sections may be suspended individually from a supporting frame preferably comprising a pair of spaced parallel horizontal beams 9| which may be detachably carried by the drum [8 as by bolting the same to angle brackets 82 upon the drum top ll. Cross bars 88 may connect the" beams 8| into a rigid framework.

To connect the heating coils'to the'supportmg beams, detachable hangers u (Figs.'2, 3 and 4) preferably in the form of non-corroding metal straps, are provided.' 'Ihese'straps are looped over. the beams and under the uppermost loops-of the. respective coil sections, and have their respective'ends connected together as by means of bolts 98 so that they can be easily removed. Preferably, .four '01 the hanger straps 94 are provided for each coil section, one at each of the four points where the latter underlies the supporting frame beams 9|. Thus, when it is desired to remove the heating coil assembly 18 as a unit, it 'is merely necessary to detach the beams 9|. from'theangle brackets 82 and lift the supporting frame and the entire heating coil assembly upwardly away from the drum I. Then any individual tube section can beremoved merely by disconnecting its four hanger straps 88 from the supporting frame. Delivery of the pumped water from the pressure duct II to the outer or first bank of heating coil sections 81 may be effected through an equalflow branch divider 88 (Figs. 1 and 4) Transfer from the first bank to" the intermediate bank.

coil sections 88' may be effected through a suitable upright header 81 to the lower end of which the discharge ends of the coil sections 81 are connected by suitable unions and to the upper end of which the inlet ends of thecoil sections 88 are connected, also preferably by suitable unions. In like mannenan upright header 88 may be provided for effecting transfer of thecirculating water and steam from the intermediat-ebank coil sections 88 to the last bank of four coil sections 88. From the latter coil sections the water and steam are conducted through a preferably L-shaped vertical and horizontalheader to the inlet end of the steam separating member 28.

Because waterabstracts heat readily compared withsteam, several measures in addition to the forced circulation are taken herein to assure constant and accelerating velocity of the water through the heating coils and freedom from stagnation or striation therein so that the heating surfaces will be constantly swept by water, and steam will be prevented from collecting in massesor patches but will, if it is present at all, be carried by thewater in the form of small, well For example, tubing of relatively small diameter is used in the heating coils to provide a relatively large heat transfer surface and to insure high velocity of the water through the tubes. Such tubing is also advantageous by reason of the lower cost per unit area of heating surface. I

Furthermore, the headers 91 and 98 by their positions and the angle of entry of the heating tubes will cause a mixing action of the entering streams of waterduet'o the abrupt commingling and. change in direction of flow. In addition,

these headers are preferably of greater cross-' sectional flow area than that of the banks of coils to which they respectively deliver, and by the same taken, are of substantially greater cross-sectional flow area than the coils from To this'e'nd the coil as v a r the latter that'even at peak demands water which which they receive,..thus reflecting additional.-

agitation and turbulence of the entering waterdue .to expansion from steaming arising from the.

being thoroughreduction in pressure,the steam v ly broken up into tiny bubbles. Then, upon delivery of the steam and water mixture to the succeeding coils, there will be an acceleration of velocity because of the steam expansion and the reduced cross-sectional flow area of the receiving coils compared with that of the header Final steaming may take place in the last header 99 may possibly arisefron the v in the drum I cannot cause surging of and in the steam. separator which are preferably of greater cross-sectional flow, area than that of the four coil sections 89 of the last bank combined. Due to thes'teaming and deceleration of the water in the header and the separator, some depositionof minerals may occur therein but this will not be great nor interfere with the optimum efliciency of the boiler" as a whole. In any event, the deposits can easily be cleaned out of the headers on occasion;

Herein the steam separating member 20 serves the. double function of. separating the steam which has been generated and also of returning the unconverted water to. the main body of water within the drum I5 substantially without agita- In the preferred form, the] tion or foaming. member 20 is of elongated tubular shape and has a cross-sectional flow area at least as large or slightly larger than the cross-sectional flow area of the header 99. Therefore, the steam can expand within'the member 20 and may easily be separated from the unconverted water. For separation the steam may escape from the member 20 through a longitudinal series of openings I00 such as transverse slots formed, in the wall thereof. Also, the separator 20preferab1y ex- 3 tends downwardly longitudinally within the-drum I5 adjacent to the vertical wall thereof, and the steam escape slots I00 are directed toward such wall in the space above the water level so that water carried therethrough by the steam will impinge against the drum wall and flow circumferentially and downwardly therealong into the; mainbody of water without agitation. Such impin ed water will cool the drum wall by absorbing end IOI project below the water level 85. In addition, the discharge or outlet end IOI is preferably constructed to direct the discharging water toward the side wall of the drum and may for this purpose be formed on a bias as shown (Fig. 2). It will be evident also that due to' the may escape from the openings I00 will not be drawn into main body of water water from the water level 35 to the steam withdrawal port I03 due to the substantial intervening space. I Should the steam pressure within the drum -I5 become excessive, it may be released through a suitable automatic safety valve I04.

The unconverted water which is returned from the steam separator 20 to the drum I5 serves as a preheating medium for the reserve supply or water within the drum and particularly for the make-up water which is supplied throughthe feed duct 32. In addition to such preheating of the water supply internally, external heat is transferred through the enclosing wall of the drum "by radiation from the'burners' I9. the" full running-conditionof the boilerthe pre- I heating may aggregate close to the criticaltemvperature of the waterxso that most of the heat absorbed by the water in passing through the heating tubes I8 will go to raisesteam.

As shown, theburners I9 are of a suitable gas fired type supplied from a manifold I05 concentric withthe drum cradle 23 (Figs 1, 2 and '7) and are=preferably equidistantly spaced from one another -'and uniformly spaced from the vertical wall ofthe 'drum I5. The, tops of the burners I9 are. located ata predetermined distance above the drum bottom I5 but substantially spacedv from the lower loops of the heating coil assembly I9, thereby providing-a substantial combustion the tops of the burners, the vertical-wall of the drum I5 and the bottom row of loops of the heating coils. A large percentage of laterally radiated heat from the burners I9 will therefore impinge upon and be transferred to the boiler water through that portion of the drum wall which is exposedtothe combustion chamber I01, without abstracting any appreciable heat'fr'om the gases of combustion which'pass up toward the heating tube assembly;I8.. Preferably the water level 35 in the drum is above the lower. row of heating coil loops so that all of-the wall area of the drum subjected to radiated andconvectedheat below the coils will'be adequately cooled. -That-portion of the drum which lies below theatops of the burners will remain substantially unheated, with the water therein practically stagnant, and thererelease of pressure by the separation and escape I of steam through the steam slots I00, the uncon-f fore will servev eflectively to collect the material or muddeposited from thewater heated in the preheating .zone thereabove, the thoroughness of thepreheatin'g assuring that most of the mineral matter and suspended material in the water will settle out in the drum. n

Fuel from a suitable source is supplied as by means of .a gas main I08 which communicates with the manifold I05 and may be provided with a gas regulator I09 which will be responsive to steam pressure within the drum I5.- To control the gas regulator I09 a pressure duct IIO may lead therefrom into communication with the water-gauge stand pipe 42.

. Alow. water shut-off valve III may be interposed in the gas main I08 as a safety measure ,to discontinue the gas supplyto the burners should the water feed to the drum I5 accidentally stop during operation. Suitable means for controlling the shut-ofl valve I I I automatically may comprise a solenoid II: having a groundedcircult. including an electrical lead II3 connected with an electrode Ill near the bottom of the water regulator tank 4| so that when the water the steam main I02. Steam that such spa'ce'or chamber I01 defined herein in part by therein falls below the safety level, the shut-off solenoid II2 will operate to close the valve III and stop the burners III to halt operation of the boiler. The solenoid H2 or other suitable gas controlling means may be utilized to shut off the gas supply if the water circulation pump 45 should stop or for some reason fail to circulate the water properly. A suitable pilot II5 communicating with the gas main I08 ahead of the shut-off valve III may be provided for lighting the burners.

Instead of the gas burners I9 suitable oil consuming burners may be relied upon as the heat source for the present boiler. For example. a blower-type of fuel oil burner may be mounted to fire substantially tangentially into the combustion chamber IIlI. Combustion air is supplied to the burners I! through the platform 25 of the base framework I8. This air will be more or less preheated by the heat thrown off by the pump motors, the circulation 'force pump 45 and the various pipe con nections which conduct the preheated water from the drum I5 to and from this pump. To assure absorption of such heat by the air, the base framework maybe substantially enclosed except under the burners is by a sheet metal sheath or casing II! which may include removable side panels II8 of which at least the one nearest the circulation pump 45 may for induced or natural draft conditions be provided with louvers III for admitting air into the base enclosure. The removable panels IIB. may be hinged, or removably hung upon hooks I20 projecting outwardly from the edge of the platform 25, and may be secured in place by means such as thumb screws I2I. Where a forced draft is desired in the boiler unit, instead of a natura1 or induced draft through the louvers IIII, a suitable fan (not shown) may be supplied in one side of the base I6.

Enclosing the combustion chamber I01 and the heating tube assembly I8, is a suitable casing I22 which in the present instance is preferably constructed of a plurality of removable sections each of which is adapted for independent removal for access to the adjacent portion of the stem generating unit. Accordingly, the casing may comprisesubstantially equally divided upper and lower annular cylindrical portions, the lower of which is divided into semi-cylindrical separable front and rear sections I23 and I24, respectively, and the upper of;which is divided into semi-cylindrical front and rear sections I25 and I23, respectively. Each of the casing sections I23, I24, I25 and I26 is preferably of a substantially standardized construction and a description of one section will therefore suffice for all. Thus, each section includes an inner shell member I23 and an outer shell member I29 (Fig. 4) having suitable insulating material therein and separably connected together in. spaced parallel relation by means of properly dimensioned coactive outwardly projecting flanges I30 and III, respec- I24 rest upon the base platform 25 and have thereto as by means of bolts I35 passing through the exposed margins of the conjoined horizontal flanges I32and I33. The'conioined vertical side flanges of the upper sections maybe secured to-"' gether similarly as the corresponding flanges of the lower sections. Through this construction it a will be apparent that any one or more of the semi-cylindrical casing sections may be removed without disturbing adjacent sections of theming or the insulation therein, and if access is desired into one of the fcasing sections, it is merely necessary to remove the outer shell I29 thereof.

Preferably, the space between the casing shells I25 and I2" wherever convenient, is utilized for such vertical connecting piping as the pressure duct I1, and the headers 51, 53 and 33. Access to such piping can be had readily by removal of the enclosing outer casing shell I29. Preferably, suitable unions are utilized in connecting such piping so that it can be easily removed when necessary. 7

A removable top closure for the casing is pro- ,vided in the present instance by a double-walled,

insulated disk-like member I31 dimensioned to flt relatively snugly into the cylindrical opening defined by the upper margins of the upper casing sections I25 and I23 and supported by an inwardly projecting shoulder flange I33 carried by said sections. Opening through the top member I31 is a flue outlet defined by an upwardly pro- .iecting flue collar I33 which is adapted to receive a suitable flue pipe I43. When access into the topof the casing is desired, the top closure member I31 can easily be lifted away. i

Preferably, the internal diameter of the upper portion of the casing I22 relatively closely approximates that of the outermost heating tube section 31 so that upward passage of the; flue gases will be closely confined to travel between the coils. Moreover, the enclosure provided by the lower portion of the casing about the fire box I II will reflect and radiate toward the preheating zone of the drum I5, heat which impinges upon the inner I tions 31 which comprise the first bank of the heating coil assembly I3, may be increased in length to extend downwardly substantially as shown in Fig. 5 along the inner walls of the lower casing sections into .the radiated heat zone. Thereby, practically no radiated heat will be lost and the confining walls of thelower casing sections will be protected against overheating and the best part oi the radiated heat which that utilized for preheating the water in the drum I5 will be used in generating steam.

superheated steam may be produced by passing the steam. from the live steam main I32 through a downcomer I which is preferably enclosed within the inner and outer shells of the casing I22 and whichfcommunicateswith a superheater I42 gas shown in Figs. 6 and 7. This superheater is preferably constructed of a plurality of loopsof pipe I43 each individually communicating with the downcomer HI. and conducting the steam in parallelpaths around the aaoasce interior of the lower casing sections it! and I24 within the most active portion of the laterally of the other tube sections. The casing which enradiated heat zone of the burners 19. After traversing the superheating circuit through the loops I43, the superheated steam may pass there- I from into a'superheated-steam main I.

which the water and steam mixture is subjected effectively avoid stagnation and striation at any point, thus assuring an exceedingly high rate of heat absorption, keeping the heating surface uniformly cool and free from sedimentation or scaling or danger of'overheating or burning out. Steam separation is effected in a highly advantageous manner which avoids passage of water into the steam mainfand effects a return of the unconverted water quietly-and without rolling of the water reserve which the returned water serves to preheat. Radiated as well as convected heat is used to utmost advantage in generating I steam as well as in preheating the boiler water,;and even the heat from the auxiliary equipment of the boiler is not wasted but is utilized for preheating the air for the burners.

It will be apparent that in generating steam in accordance with the above method the emclency of the generating unit can be maintained substantially uniform throughout its entire operating range. Due to the accurate control of circulation provided, the rate of flow of water over the heat transfer surfaces can be regulated so as to provide the optimum rate of heat absorption for any rate of heat input. Thus, when the unit is operated at maximum capacity, that is, when the'maximum amount of heat is supplied, the rate of circulation may be increased by speeding up the circulating pump. On the other hand, when the heat supply is reduced, the rate of circulation may be correspondingly reduced so that the conversioneillciency remains substantially at the maximum point. 7

To practice the novel method, a new self-con- Y tained automatic steam generatorhas been provided which is exceptionally economical infloor space and headroom since the whole unit can be embodied in a small vertically arranged structure in which practically all of the auxiliary equipment'is housed within the base under the Y steam generating part of the unit. No special settings or boiler pit are required, but the unit can be placed wherever the small amount of room required is available therefor, and where it is gas fired it need not even be connected with a stack. because where ,no' stack is available for inducing natural draft, forced draft may very easily be applied. Because of the negligible exterior tem- 'peratureof the outer casing the unit can be housed in places not ordinarily practicable for a boiler. But one drum is required and that will serve as a combined water reservoir, preheater, mud drum, steam separating chamber, and steam chest. In addition, the drum supports the heating tube assembly from which any one of the plurality of tube sections can be easily removed if .steam and water and the frequent agitation to closes the unit can easily be opened by the removal of selected sections for access into any portion of the unit. Other parts of the unit are also easily removable. Withal the unit is adapted forunusually long periods of continuous operation at high output with undiminished efficiency and without requiring special attention. Ample safety features are embodied in the unit to avoid danger of overheating should any vital mechanism fail; and although it is hardly likely that any heating tube coil should ever burn out or break, yet if it does no danger will be encountered from escapingsteam due to the very limited amount that would be released.

' As a practical'example, an actual installation embodying the principles ofthe invention in a steam generating unit approximately thirty inches in diameterupon a base three'and one-half feet square andhaving anover-all height of about five and one-half feet has'been operated over an extended periodto generate about one thousand temperature of the fluid flowing therein. In this pounds of steam per hour continuously at'a normal working pressure of about one hundred twenty-five pounds per square inch and a maximum of two hundred fifty pounds per square inch.

This unit has an over-all thermal eiiiciencyaveraging eighty-five percent, without the use of a preheater or economizer, and has unusually large overrating since it generates one boiler horsepower for about every one and one-half square feet of heating surface. The steam and water drum or this-unit is a tube of ten inch diameter providing a water reserve of about six gallons while the heating coils comprise a total of about two hundred fifty lineal feet of' one-half inch standard pipe size seamless tubing having, together with the accessory pipingyla ca'pacity'of about an additional six gallons. Due to the high velocity of water'through the tubes, namely, such as to effects. complete turnover of water in the entire system every two minutes, the heat transfer constant, that is, the ratio of heat transfer per unit area of the tubes, taking into consideration the thickness and temperature difference of the material forming the same, has been about fifty as compared with a range of from three to fourteen customarily found 'in the heat transfer surfaces of prior water tube boilers. The actual temperature of the tubes at any" point in the assembly has been found to be just afew degrees above the unit, the water has beencirculated at approximately three'times the maximum speed of evaporation. Over an extended period of time sedimentation orscaling in the heating tubes has been negligible and no cleaning has been required although untreated relatively hard water has been used. Oil in the water, as may come from the circulation pump, has no detrimental effect upon thermalefllciency'of the'unit, th volatile constituents apparently passing off 'with the steam and the remainingsludge collecting in the mud sump of the Water drum. Sedimentation has been almost completely confined to the bottom of the central drumd'rom which the muddy deposit is blown oil at intervals. In operation this unit has been almost perfectly silent. In commencing operation from a cold state, the burners can beat once fired fully without in anywise endangering any part of the unit and a full head of steam has been obtained within a few minutes after starting,

I claim as my invention:

necessary without altering the suspension of any 1. A steam generating unit comp ising, combination, a base, an elongated drum supported in a vertical position on said base, a heating tube assembly encircling the upper portion of said drum, combustion means disposed in heating relation to said drum and to said tube assembly, a casing enclosing the drum, the combustion means and the tube assembly for confining the products of, combustion to an upward path through the tube assembly, means for feeding water into said drum including a pump and control means therefor operative to maintain a predetermined level of water within the drum rising at least as high as the bottom of said tube assembly, means for circulating the water from said drum through the tube assembly including a pump operative to force the water through the tube assemblyat a predetermined velocity, both of said pumps being of double stroke action adapted to pump the water with substantially continuous pressure and without surging, and a connection from said tube assembly to the upper portion of said drum for returning the water to the drum after its passage through the heating tube assembly.

2. A steam generating unit comprising, in combination, a cylindrical water drum, a series of concentrically coiled tubes encircling the upper portion of said drum, said tubes being arranged in groups having progressively increasing over-all cross-sectional areas, headers connecting adjacent groups of tubes to provide a continuous flow passage communicating with the upper portion of said drum, means for heating said drum and said tubes, means for supplying water to partially fill said drum, and'a pump arranged to withdraw water from said drum and to circulate it through said tubes at such a velocity and in such volume that only a relatively small portion of the water is converted into steam upon its return to the drum,

the remainder of the returned water being mixed with the water in the drum for recirculation combination, a water chamber, means for sup plying water to said chamber, a plurality of concentric helical heating coils encircling said chamber and connected therewith, said coils being arranged in groups of progressively increasing aggregate flow area to accommodate steam expansion, headers connecting successive groups of coils to provide a continuous passage for water to be converted'into steam, means for heating said coils and said chamber, power actuated means for withdrawing water from said chamber and forcibly circulating it through said coils to absorb the heat imparted to the coils by said heating means whereby to convert a portion of the water into steam. I

' 6. A steam separator for a steam generating unit wherein the water is heated to steaming temperature and delivered into a partially filled water drum, said separator comprising an elongated hollow member having its discharge end adapted to project into the body oi water within fer area from the outer to the inner section, and v I 'means connecting said coils into a continuous drum, a heating tube assembly surrounding the upper portion of said drum, means supporting said tube assembly on the drum, heat supply means disposed in heating relation to said drum and said tube assembly", a feed pump for supplying water to said drum, and a pump for circulating water from the drum through said tube assembly and back to the drum to convert a portion of the water into steam, said drum, said heat supplying means and said pumps being mounted on said base to form a unitary structure.

4. A steam generating unit comprising, in combination, a base, an elongated drum supported in a vertical position upon said base, 3

tion of said drum, said tube assembly communicating with the upper portion of said drum, combustion means disposed below said tubeassembly in heating relation to said drum and to the tube assembly, a casing enclosing. the drum, the tube assembly and the combustion means operative to confine the products of combustion platform, heat transfer means'above said platseries of unidirectional parallel-flow banks progressively increasing in number of coils from the outer to the inner bank so as to provide substantially equal heat transfer areas for each of said banks.

8. In a steam generating unit, in combination, a heating tube asembly comprising a plurality of concentric coils of .tubing, headers connecting said coils in groups progressively increasing in number of coils per group to provide a series of parallel flow passages, means for passing heated gases over said coils in one direction, and means for circulating water through the passages provided by said groups of coils counterflow to the passage of heated gases over the coils to'absorb the heat imparted thereto by the gases.

9'. A steam generating unit comprising, in combination, a base structure including a raised form including a water reservoir, a burner mounted on said platform for heating said heat transfer'means, means for circulatingthe water from said reservoir through the remainder of said heat transfer means including a pump heating tube assemblyencircling the upper portubes with the succeeding bank positioned to ef- -fect an abrupt change in the direction of flow of the entering water and steam mixture, each of said headers having a greater flow area than the bank of tubes to which it discharges so as to permit a partial conversion of the water into said coils, and means for steam and thus effect delivery of the steam and water mixture to the succeeding bank of tubes with increased velocity.

11. A steam generating unit comprising, in combination, a vertically mounted combined water reservoir and steam separating drum, means for supplying water to fill said drum only partially, a plurality of concentric helical heating coils encircling the upper portion of said drum, said coils being arranged in a series of successive groups of progressively increasing aggregate flow area, means for supplying heat adjacent to the lower portion of said drum for preheating the Water therein and for heating said coils, means for withdrawing water from said drum and forcibly circulating the water through said coils, means forming at least part of the flow path from group to successive group of said coils constructed and arranged to permit limited flashing of steam to boost the speed of water flow through the successive group of coils, and means connecting the group of coils through which the water flows last with the top of said drum for separating steam from the water.

12. A steam generating unit comprising, in combination, a water chamber, means for feeding water to said chamber to maintain a substantially constant level of water only partially filling the chamber, a continuous series of heat transfer coils surrounding the unfilled portion of said chamber while leaving the lower portion of the chamber free, one end of the series communicating with the water-filled portion of said chamber to receive water therefrom and the other end of the series communicating with said unfilled portion to discharge the water thereinto, means for forcibly circulating the water through simultaneously heating the water-filled portion of said chamber and said coils.

13. A steam generating unit comprising, in combination, an upright drum, means for maintaining a body of water partially filling said drum, a casing enclosing said drum in radially spaced relation, a massed series of heating tubes substantially filling the space between saidcasing and the upper unfilled portion of said drum, a heat source under said heating tubes in the space between said casing and the lower waterfilled portion of said drum for preheating the water in said drum and for heating said tubes, said tubes being arranged to force the heat from said source to travel upwardly in sinuous paths portion of said drum and adapted to be therethrough and serving to protect said upper unfilled portion of said drum against overheating, and means for connecting one end of said series of heating tubes for receiving water from the body of water in said drum and the other end of the series for discharging the heated water into the upper unfilled portion of the drum for separation of steam.

14. A steam generating unit comprising, in combination, an upright drum, means for maintaining a body of water partially filling said drum, a casing enclosing said drum in radially spaced relation. a mass of heating tubes substantially filling the space between said casing and the upper unfilled portion of said drum and leaving the lower water-filled portion free, a heat source under said heating tubes in the space between said casing and said lower waterfilled portion of said drum for preheating the water in said drum and for heating said tubes, said tubes being arranged to force the heat from said source to travel upwardly in sinuous paths therethrough and serving to protect said upper unfilled portion of said drum against overheating, means for connecting said heating tubes for receiving water from the body of water in said drum and for discharging the heated water into the upper unfilled portion of the drum for separation of steam, and a superheater comprising an arrangement of coils mounted adjacent to said casing opposite the water-filled portion of said drum and below said heating tubes connected to receive steam from the upper unfilled heated by radiated heat from said heat source. I

15. In a steam generating unit, in combination, a heating tube assembly comprising a plurality of tubes arranged in concentric coils, means for supplying heat to said tube assembly, power actuated means operative to forcibly circulate water through the tube assembly, and headers connecting successive coils from the outside to the inside of the assembly in series by groups to provide a plurality of banks of parallel flow passage, each of said headers providing a larger cross-sectional flow area than the tubes from which circulating water is supplied thereto so as to permit a partial conversion of the water into steam with resultant expansion whereby the water is delivered to the succeeding tubes with increased velocity.

' CHADWELL OCONNOR. 

